I've cleaned the throttle body flap and the IACV. If the engine is cold it runs about 1000rpms even with the AC blower and compressor on. As it warms up the idle begins to fluctuate between about 500 or a little lower and up to 1000rpms. When I turn the AC off and the blower off it idles beautifully at about 700rpms. If I turn just the blower on and not the AC it idles at about 500 and runs pretty steady there but may idle up to 600 or so. If course, all of this is while it's not moving and I'm giving it no gas.

Not sure what else to check unless the IACV is just bad. Is there an easy way to check that? The coolant hoses and the electrical connections are a buggar to get to for a short person.

 

Does the 1999 CRV have a mass airflow sensor?

 

No it does not, it has a MAP sensor.

 

Could a bad MAP sensor be the cause of the erratic idle or drop in rpms when the AC is on?

 

I'd lean more towards the AC system being the culprit. The compressor engages, the condenser fan kicks on and it's now drawing more power. I would do a search for an AC Idle UP switch or something of the sort which may be faulty and causing your idle to drop too much rather than kick up when the compressor and fan kick on.

 

OK. I'll check that.